ABSTRACT (Biomedical Research) Research Project 2 Biomedical Research Project 2 is one of two biomedical research projects proposed for the ?Center for Environmental and Health Effects of PFAS? being led by North Carolina State University (NC State). The primary goal of the proposed Center is to provide highly relevant data and information to help the Superfund Research Program (SRP) address the growing problem of per- and polyfluoroalkyl substance (PFAS) contamination across the United States (US). PFAS are considered contaminants of emerging concern for myriad reasons, but one of the most pressing is that only a handful of the nearly 5,000 PFAS that are known to exist have been evaluated for their toxicologic potential, even though numerous communities are being impacted by their presence in environmental media, especially drinking water. Studies of humans exposed to perfluoroocatonic acid (PFOA) and perfluorooctane sulfonate (PFOS), two PFAS detected with high frequency and concentration in human and environmental samples, have provided compelling evidence that the immune system is a sensitive target of PFAS. Additional work with experimental animal models supports the hypothesis that PFAS induce immunotoxicity and alter responses of both the adaptive and innate immune systems. While PFOA and PFOS are presumed to be immune hazards to humans, several gaps in knowledge exist: notably, the mechanism(s) by which these PFAS induce immunotoxicity remain elusive, and the extent to which most PFAS of emerging concern perturb immune function is largely unknown. Therefore, the objectives of Project 2 are twofold: i) explore molecular changes underlying PFAS-induced immunotoxicity in select animal models as well as human cell lines to identify impacted signaling pathways and networks, and ii) determine the immunotoxicological profile, including mechanistic underpinnings, of PFAS of emerging concern relative to the few well-studied PFAS. Our global hypothesis is that PFAS-mediated immune suppression results from modulation of immune cell metabolic functions. This hypothesis will be evaluated by (Aim 1) quantifying the impact of PFAS exposure on B cell development and antibody production in a mouse model and (Aim 2) identifying the impact of PFAS exposure on phagocytotic cell function using a zebrafish in vivo model and human in vitro cell line models. This project will address significant gaps in what is known about the mechanisms by which PFAS induce immunotoxicity, which will improve management of a known PFAS health risk, immune suppression, and accelerate development of immune therapies for affected individuals. Additionally, the large number of untested PFAS also means that methods for rapid prioritization are critical for informing appropriate regulatory measures; our project will uncover molecular initiating events underlying altered immune responses to facilitate novel, immune-mechanism-based prioritization strategies for PFAS recently detected in North Carolina and elsewhere.